The current article demonstrates the geoeffectiveness of solar flare associated Coronal mass ejection (CME) accompanied with Deca-hectometric (DH) type II radio bursts by comparing the set of events in the rising phase of solar cycle 23rd (1996–2001) and 24th (2009–2014). Our observations are: (i) Solar cycle 23rd have high Dst index than the solar cycle 24th except for the year 1999. (ii) Dst has its peak between 3rd to 5th day after the CME onset for both the solar cycles. (iii) The correlation coefficient between Interplanetary magnetic fields (IMF) and Dst is good for both the solar cycles. (iv) Solar cycle 23rd have very strong correlation between CRI and Dst as compare to solar cycle 24th. Thus, our predictions show that solar cycle 23rd is more geoeffective than solar cycle 24th.

We investigate the association of the cosmic-ray intensity (CRI) with the interplanetary magnetic field (IMF, B) and geomagnetic storms (GS) for the period 1997 -2006 (Solar Cycle 23). To do this, we conducted a Chree analysis by the superposed-epoch method. A transient decrease in CRI is found on the occurrence days of GS, and this decrease shows a similar pattern to that of the disturbance storm-time index (Dst). In addition, we show that the CRI decreases with the increase in IMF. The time lag between the decrease in CRI and increase in IMF is about one day or less. Furthermore, an increase in IMF B is found with the decrease in Dst index. IMF and Dst index are highly anti-correlated to each other, while the sunspot number is not found to be correlated with IMF, Dst index, or CRI for the period studied. The IMF is found to be an effective parameter combination for producing GS and Forbush decrease. We also found two types of decrease in CRI for Solar Cycle 23: i) symmetric and ii) asymmetric decreases. The study of CRI decreases may be useful for studying space-weather effects.

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In the present study we have selected 131 events of the flare-CME accompanied by type II radio burst chosen during the period from 1996 to 2012. Statistical analyses are performed to examine the distribution of solar flares with respect to CME span and it was found that from 131 events only 49 lie under the CME span, whereas 82 events are outside the CME span. Our analysis indicates that flare-CME accompanied by type II radio burst does not follow the CSHKP flare-CME model. Under the CME span, 57% events occurred in the northern region and 43% events in the southern region, whereas outside the CME span 51% events occurred in the northern region and 49% events in the southern region. The northern and southern hemispheres between 10 to 20 o latitudinal belts are found to be more effective in producing events. We also found that under the CME span the maximum number of events resided at the center, and outside the CME span all the 82 events spread out to one particular side.

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